More pitch = more speed, and less static thrust.
Less pitch = less speed, and more static thrust.
High pitch is good for propjets, quickies, and other speedy types.
Got a funfly? Stick with a pitch in the 4-6 range.(for .40 sized planes)

You didn't say which engine you're running.
For your average sport 45-46, I'd say try an 11x5 APC. It's my favorite so far,
for a 3.5-5lb plane with an OS 46 installed. Others like the 12.25x3.75.
Your mileage may vary. Depends on the plane, the engine, the weather, and your altitude,
to name a few factors. Maybe purchase a few different props and experiment.
(11x5, 11.5x4, 12x4, 12.25x3.75, are probably all good to try, for a decent .46)
There are differences between makes and widths, too. Use what makes you happy